Interface between cellular and wired networks with enhanced subscriber mobility

ABSTRACT

A system to enable communication between a base station controller (24) within a cellular network (12), and a wired telephone system (38, 39) in a wired subscriber loop (113), wherein the base station controller (24) is responsive to, and generates, cellular network signaling, and the wired telephone system is responsive to, and generates, wired signals. The system includes: a protocol processor (121) receptive to the wired signals, for generating processed signals; and a terminal adapter controller (34) conductively coupled both to the base station controller (24) and to the protocol processor (121), receptive to the processed signals, for generating cellular network signaling. In another feature of the invention, the cellular network signaling is GSM signaling. In another feature of the invention, the system also includes a voice service module (123) conductively coupled to the protocol processor, for compressing voice data to standard cellular compression. In another feature of the invention, the system also includes means (150) for converting mobility events in the wired telephone system to cellular network signaling.

TECHNICAL FIELD

The invention relates generally to cellular communication networks and,more particularly, to wired access to a cellular network.

BACKGROUND OF THE INVENTION

As cellular telephone service has increased, a need has arisen for asingle telephony system that can service a subscriber both at his home,that is, fixed-base, or stationary, and when he is away from home, ormobile.

U.S. Pat. Nos. 5,412,760 and 5,528,665, issued to Peitz, describe atelephone system for both mobile and stationary subscribers, in whichthe stationary subscribers are not assigned permanent channel pairs, butrather are treated as the mobile subscribers, and are assigned channelpairs at the time a telephone connection is made. All connection channelpairs are within the frequency spectrum of the broad band cableconnecting the stationary subscribers.

However, the Peitz patents do not contemplate using unshielded copperpair telephone lines normally used for ISDN basic rate service. Rather,they teach installing new digital, preferably fiber optic, cables tosubscribers' homes.

Analog cellular telephone service originally developed independently invarious countries, each country's equipment and service incompatiblewith the others'. The Europeans eventually agreed on standards fordigital cellular telephone service, called "GSM" ("Global System ForMobile Communications"). The European Telecommunication StandardsInstitute (ETSI) published phase I of the GSM specifications in 1990.ETSI published some GSM Technical Specifications, version 5.1.0, inMarch, 1996.

A need exists for a single telephone system for both mobile andstationary subscribers, which uses unshielded copper pair telephonelines normally used for ISDN basic rate service, and which is compatiblewith the GSM standards.

SUMMARY OF THE INVENTION

The present invention, accordingly, provides a system and method toenable communication between a base station controller within a cellularnetwork, and a wired telephone system in a wired subscriber loop,wherein the base station controller is responsive to, and generates,cellular network signaling, and the wired telephone system is responsiveto, and generates, wired signals. The system comprises a protocolprocessor receptive to the wired signals, for generating processedsignals; and a terminal adapter controller conductively coupled both tothe base station controller and to the protocol processor, receptive tothe processed signals, for generating cellular network signaling.

In another feature of the invention, the cellular network signaling isGSM signaling. In another feature of the invention, the system alsoincludes a voice service module conductively coupled to the protocolprocessor, for compressing voice data to standard cellular compression.In another feature of the invention, the system also includes means forconverting mobility events in the wired telephone system to cellularnetwork signaling.

The invention achieves a technical advantage in that it provides thesame services to wireline subscribers as it provides to mobilesubscribers.

The invention achieves another technical advantage in that it usesexisting local loop with services provided by an existing MSC, so thatan operator has to add neither wireline switching capabilities, nor usecellular radio frequency transmission spectrum for local loop service.

The invention achieves another technical advantage in that it providesstandard interfaces for analog and ISDN BRI telephone sets, so thatsubscribers may use their existing telephone sets.

The invention achieves another technical advantage in that it complieswith the A-bis interface from a base transceiver station to a basestation controller, so that there is no change required in theconstruction or operation of 1) the base station controller, and 2) amobile services switching center.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the GSM wired access system of the presentinvention.

FIG. 2 is a schematic, in block diagram form, of the TA 36 of FIG. 1.

FIG. 3 is a schematic, in block diagram form, of the TAC 34 of FIG. 1.

FIG. 4 is a table listing the combination of ISDN protocols and GSMprotocols used to carry signaling information.

FIG. 5 is a flow chart of the algorithms used by the TA 36 when it ispowered on.

FIG. 6 is a flow chart of the algorithms used by the TA 36 when it ispowered off.

FIG. 7 is a flow chart of the algorithms used by the protocol processor121 when a subscriber places a call.

FIG. 8 is a flow chart of the algorithms used by the protocol processor121 when a subscriber is called.

FIG. 9 is a flow chart of the algorithms used by the protocol processor121 when the activate SIM switch 150 is deactivated.

FIG. 10 is a flow chart of the algorithm used by the TAC 34 whenprocessing incoming messages.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This description uses the following abbreviations:

2B+D see BRI

BRI ISDN Basic Rate Interface; 144,000 bits per second, two bearerchannels, and one D channel

BSC Base Station Controller

BTS Base Transceiver Station

EFR Enhanced Full Rate

ETSI European Telecommunication Standards Institute

GSM Global System For Mobile Communications

GSM₋₋.₋₋ ETSI GSM Technical Specification₋₋.₋₋

HLR Home Location Register

HSCSD High Speed Circuit Switched Data

IMSI International Mobile Subscriber Identity.

ISDN Integrated Services Digital Network

ISDN Q.921 ITU-telecommunications recommendation for Layer 2 BasicAccess User-to-Network Interface. Q.921 is commonly used as a referenceto the interface specified by ANSI T1.602-1989.

ISDN Q.931 ITU-telecommunications recommendation for Layer 3 basic callcontrol. Q.931 is commonly used as a reference to the interfacespecified by ANSI T1.607-1990.

LAC Location Area Code

LAPDm Link Access Protocol For The Mobile D Channel

LEC Local Exchange Carrier

MSC Mobile Services Switching Center

MS Mobile Subscriber

MSISDN Mobile Subscriber ISDN Number

OAM Operations, Administration, and Maintenance--network managementfunctions

OMC-R Radio Operations and Maintenance Center

OMT Operations and Maintenance Terminal

PLMN Public Land Mobile Network

POT Plain Old Telephone, one example of a "Set"

SIM Subscriber Identity Module, a "smart" card inserted into a mobiletelephone. The SIM contains subscriber-related data.

SOHO Small Office/Home Office

TCU Transcoder Unit

TA Terminal Adapter

TAC Terminal Adapter Controller

TCH Traffic Channel

VLR Visitor's Location Register, a local database to an MSC forregistering visiting mobile station users.

For definitions of other abbreviations, and definitions of other terms,see Newton's Telecom Dictionary, 11th edition, 1996.

Referring to FIG. 1, the GSM wired access system 10 of the presentinvention includes a PLMN 12, a wire center 14, and a SOHO or residence16. The PLMN 12 has an HLR 18, which connects to an MSC 20. The MSC 20connects via an A-i/f interface 21 to a TCU 22. The TCU 22 connects viaan A-ter interface 23 to a GSM network's base station controller ("BSC")24. An Operations and Maintenance Center for the Radio ("OMC-R") 26 alsoconnects to the BSC 24. The BSC 24 connects to a BTS 28. The BTS 28connects via an air interface 29 ("wireless signals") to a wireless set,"GSM MS" 30.

The wire center 14 has LEC switching equipment 32 and a GSM wiredterminal adapter controller ("TAC 34"). The TAC 34 connects to both theBSC 24 and an operation and maintenance terminal ("OMT") 27. Althoughthe OMT 27 is shown as located in the PLMN 12, it could be locatedanywhere. The TAC 34 connects via an A-bis interface 35 to the BSC 24.The SOHO 16 has one or more GSM wired terminal adapters ("TA 36"), whichconnects to the TAC 34 via an ISDN BRI compatible subscriber loop 37.The TA 36 also connects to an ISDN set 38, and an analogset-with-an-ISDN-adapter 39. In a oversimplified sense, the TAC 34 is aBTS with wired connections to the TA 36, which functions like an MS.Together, the TAC 34 and the TA 36 are means for converting wiredsignals to cellular network signaling.

GSM Wired Terminal Adapter Controller (TAC 34)

Referring now to FIG. 2, the TAC 34 connects several TA's 36 (althoughonly one TA 36 is shown in FIG. 1) to the BSC 24. The TAC 34 containsseveral line modules 211 which terminate the wired subscriber loops 37connecting the TA's 36 to the TAC 34. The TAC 34 also contains an A-bisinterface module 213 which presents the standard GSM A-bis interface tothe BSC 24 as described in ETSI GSM Technical Specifications for GSMA-bis Interface:

GSM 8.51, Version 4.1.0, March 1995;

GSM 8.52, Version 4.2.0, August 1995;

GSM 8.54, Version 5.0.0, December 1995;

GSM 8.56, Version 4.0.2, September 1994; and

GSM 8.58, Version 5.2.0, July 1996.

The TAC 34 also contains a switching module 212, an operations andmaintenance terminal interface 220, and a terminal adapter controllerapplication 214 (shown in FIG. 10).

At each line module 211, the D-channel and the two B-channels from a TA36 are separated into as many as nine separate connections (1 signalingchannel and 8 traffic channels--4 traffic channels from each B-channel)to the switching module 212. The switching module 212 dynamicallyswitches a traffic channel from a line module 211 to the proper circuitof the A-bis interface module 213. The switching module 212 performsthis connection switching each time the BSC 24 assigns a channel to theTA 36 in response to a channel request from the TA 36. The terminaladapter controller application 214 determines how to make the connectionby looking at the contents of the GSM RIL3-RR channel request and GSMRIL3-RR channel assignment messages to see which circuit the BSC 24 hasassigned to the TA 36 for a particular call. The terminal adaptercontroller application 214 looks at the GSM RIL3-RR channel releasemessage to see when the circuit is released so that it can instruct theswitching module 212 break the connection. The TAC 34 does not alter thecontents of any of these messages. During each call, the TA controllerapplication 214 stores information from these messages in order toproperly instruct the switching module 212 to switch the traffic channelfor that call. The TA controller application 214 instructs the switchingmodule 212 via the control link 222 as to when a traffic channel from aline module 211 should be connected to a circuit on the A-bis interface213, and when the connection should be broken.

In addition to traffic channel switching, the TAC 34 transfers signalingmessages, which are transmitted on the D-channel between the TA 36 andthe line modules 211, to the proper circuit on the A-bis interfacemodule 213. The switching module 212 connects a D-channel from a linemodule 211 to the TA controller application 214 through a signaling link224. The TA controller application 214 multiplexes the messages receivedon all the signaling links 224 to the A-bis interface module 213. The TAcontroller application 214 transmits the multiplexed messages to theA-bis interface module 213 via the signaling link 223.

Signaling messages from the BSC 24 are transmitted to the TA controllerapplication 214 by the A-bis interface module 213 across the signalinglink 223. The TA controller application 214 transmits each of thesemessages on the signaling link 224 that is connected to the proper linemodule 211. The switching module 212 connects each signaling link 224 toa line module 211 as instructed by the TA controller application 214.The TA controller application 214 maps each signaling message receivedon the signaling link 223 to a line module 211, and the signaling link224 connected to that line module 211, by examining the the LAPDterminal endpoint identifier in the message.

The TA controller application 214 also monitors the status of each linemodule 211 through a control link 221.

The TAC 34 transmits unaltered all messages it receives from the TA 36to the BSC 24. Conversely, the TAC 34 transmits unaltered all messagesit receives from the BSC 24 to the appropriate TA 36, with oneexception. When the TAC 34 receives a GSM RIL3-RR cipher mode message,it immediately replies with the GSM RIL3-RR cipher mode complete messageto the BSC 24. Thus, it is transparent to the BSC 24 and the MSC 20 thatno ciphering is performed between the TA 36 and the TAC 34. Ciphering isunnecessary on the wired subscriber loop because the transmission onthis loop cannot be intercepted over the air. Ciphering is normally donebetween a GSM mobile station and a GSM BTS such that the over-the-airtransmission is not understandable by anyone intercepting thetransmission.

The A-bis interface module 213 is a telephony trunk circuit interfacethat manages several circuit groups that connect the TAC 34 to the BSC24. The TA Controller Application 214 monitors and controls the A-bisinterface module 213 through the signaling link 223.

The terminal adapter controller application 214 also performsmaintenance and administrative operations as directed by the operationand maintenance terminal 27. This includes loading software, changingconfiguration parameters, and reporting the status of line modules 211and A-bis interface module 213.

GSM Wired Terminal Adapter (TA 36)

Referring now to FIG. 3, the TA 36 includes as functional components aGSM/ISDN protocol processor 121, an ISDN S/T bus interface 120, a voiceservice module 123, a U' Interface 124, a GSM subscriber identity moduleinterface 122, and a switched SIM interface 125.

The protocol processor 121 contains protocol processing logic whichconverts wired signals (ISDN Q.931 messages) from the S/T bus interface120 into GSM radio interface layer 3--call control messages which arepassed to the U' Interface 124. It also converts GSM radio interfacelayer 3--call control messages from the U' interface 124 into wiredsignals (ISDN Q.931) messages which are passed to the S/T bus interface120 over a control and signaling link 142.

The protocol processor 121 generates (1) GSM radio interface layer3--mobility management (RIL3-MM) messages in response to mobility eventsdetected in the SOHO 16, and (2) GSM radio interface layer 3--radioresource (RIL3-RR) messages. Both types of messages are sent to the TAC34 via the U' Interface 124.

The protocol processor 121 also receives and processes GSM RIL3-MM andGSM RIL3-RR messages received from the GSM TAC 34 at the U' Interface124. GSM 4.08, version 5.3.0, release date July, 1996, which isincorporated herein by reference, describes the processing of thesemessages. These messages are not passed on to the S/T bus interface 120or to any terminal attached to the S/T bus interface 120.

The GSM/ISDN protocol conversion and GSM RIL3-MM and -RR protocolprocessing performed by the protocol processor 121 allows the TAC 34 tocomply with the A-bis interface 35. This A-bis interface complianceenables the TAITAC wired access system to be added to an existing GSMwireless network with no hardware or software modifications to the BSC24, the MSC 20, the HLR 18, and the VLR 19.

GSM RIL3 mobility management messaging allows the GSM network to locatea particular SIM inserted in any TA 36 using the existing GSM networklogic for locating a SIM in a mobile station. This means that thedirectory number used to call a telephone set attached to a TA 36 can bechanged simply by replacing the SIM in the TA 36. Furthermore, a TA 36can be moved from one physical location to another and, assuming thatthe subscriber loop at the new location is connected to a TAC 34, the TA36 can be connected and will operate in the new location with the samedirectory number as in the old location. This is accomplishedautomatically by the GSM network using existing GSM mobility managementprocedures with no human interaction by the network operator.

The GSM RIL3-RR messages are transmitted between the TA 36 and BSC 24unaltered by the TAC 36, but the TAC 36 looks at certain GSM RIL3-RRmessages to see how to allocate the traffic channels on the subscriberloop 37.

The protocol processor 121 uses the signaling connection 146 to controland monitor the U' Interface 124, as well as sending and receivingD-channel information (signaling messages) that is transmitted andreceived by the U' Interface 124.

The voice service module 123 provides several digital signal processingcapabilities, but primarily it functions as a GSM enhanced full ratevoice encoder/decoder complying with GSM 6.51, version 5.1.0, releasedate March, 1996. The voice service module 123 compresses the digitallyencoded voice signal from the normal 64 kbps wireline rate to the GSMstandard 16 kbps full rate. The voice service module 123 functions as ameans for compressing voice data to standard cellular compression.

Both the B-channels of the U' Interface 124 operate at 64 kbps, whilethe voice service module 123 encodes each conversation at 16 kbps. Thismeans that the U' Interface 124 can support up to eight simultaneousconversations at 16 kbps each. In the preferred embodiment, however, thevoice service module 123 just rate adapts each 16 kbps voice channel toa 64 kbps B-channel on the U' Interface 124.

In an alternate embodiment of the GSM Wired Terminal Adapter thatenables more than two simultaneous conversations, the voice servicemodule 123 is responsible for multiplexing the 16 kbps conversationsonto the 64 kpbs B-channels to the U' Interface 124. In GSM terms, eachconversation is referred to as a "traffic channel". So, each B-channelcan carry up to four traffic channels multiplexed on it, for a total ofeight conversations per TA 36. However, an ISDN S/T bus such as an ISDNS/T bus 113 can support only two B-channels (two simultaneousconversations/data calls).

In the alternate embodiment that uses more than two traffic channels perTA 36, the TA 36 must be constructed with multiple SIT buses, up tofour, and each S/T bus is assigned two of the eight traffic channels.

Standard ISDN sets 38 and standard analog-to-ISDN adapters 116 connectto the S/T bus interface 120, which supports the standard ISDN S/T bus113 defined in ANSI standard T1.605. (ANSI T1.605-1991, ISDN BasicAccess Layer 1 Interface at S and T Reference Points, corresponds toITU-T Recommendation 1.430). The S/T bus interface 120 separates theB-channel information from the D-channel signaling information cominginto the TA 36 on the S/T bus. The S/T bus interface 120 connects to thevoice service module 123 via a connection 140, over which B-channelinformation passes. B-channel transmission links 140 and 144 carrydigitally encoded voice or bearer data (for data transfer use by datacalls). The B-channel information passes through the voice servicemodule 123, via the link 144, to the U' Interface 124. When a B-channelis carrying data, the protocol processor 121 instructs the voice servicemodule 123 not to perform EFR voice compression, but to rate adapt thedata transfer to 16 kbps. D-channel signaling is transmitted to theprotocol processor 121 over the separate signaling and controlconnection 142.

The U' Interface 124, under control of the protocol processor 121,multiplexes the D-channel information and B-channel information onto thesubscriber loop 37 connecting the TA 34 to the TAC 36 in the same manneras a standard ISDN U interface. As on the standard ISDN U interface, oneD-channel and two B-channels are transmitted on the subscriber loop 37.However, in the preferred embodiment, each B-channel can carry up tofour traffic channels.

FIG. 4 shows the combination of ISDN basic access protocols (Layer 1 andLayer 2) and GSM 4.08 protocols (Layer 3) that are used to carrysignaling information on the D-channel of the subscriber loop 37.

Referring back to FIG. 3, all transmission between the TA 34 and the TAC36 passes through the U' interface 124. ANSI Standard T1.601-1992, ISDNBasic Access Layer 1 User-to-Network Interface is the BRI physicalinterface implementation for the subscriber loop 37 made up of a singlepair of wires, which is normal in North America.

The SIM Interface 122 accepts a normal GSM subscriber identity modulecard or plug-in module as described in GSM 11.11, Version 5.3.0, July1996, which is incorporated herein by reference. The SIM interface 114is a standard interface. GSM 11.11 describes the physical, electricaland functional specifications of the SIM interface 114.

A SIM 111 is associated with the subscriber's directory number by theGSM network. The presence of a SIM in the TA 36 allows the GSM networkto deliver calls to the subscriber whose SIM is associated with thedialed directory number. A SIM must be in place at the SIM interface 122in order for the TA 36 to originate or terminate telephone calls. Asignaling link 148a connects the protocol processor 121 and the SIMInterface 122. A similar signaling link 148b connects the protocolprocessor 121 and the switched SIM interface 125.

In the preferred embodiment, the TA 36 has a SIM 111a plugged into theSIM Interface 122, and a SIM 111b plugged into the switched SIMinterface 125. Both SIM's are associated with each ISDN terminal on theS/T Bus 113. This means that a call to the directory number associatedwith either SIM will cause all telephone sets connected to the S/T Bus113 to ring.

In an alternate embodiment, multiple SIM's are installed at both the SIMInterface 122 and the switched SIM interface 125.

The switched SIM interface 125 accepts a SIM card or a plug-in SIM,using the SIM interface 114, which is described in GSM 11.11, Version5.3.0, July 1996. The switched SIM interface 125 connects to an activateSIM switch 150 via a switch circuit interface 152 which carries anon/off or activate/deactivate signal. When the activate SIM switch 150is in an off/deactivate state, the switched SIM interface 125 willindicate to the protocol processor 121 that the SIM is not installed.The activate SIM switch 150 functions as a means for converting mobilityevents in the wired telephone system to cellular network signaling. Inaddition to the signalling link 148b, the switched SIM interface 125also has a switch circuit connection 154 to relay the on/off state ofthe activate SIM switch 150 to the protocol processor 121. When theactivate SIM switch 150 is turned on, the protocol processor 121 willactivate the SIM using the TA power up procedure described elsewhere inthis document, as if the TA 36 had just powered on. When the activateSIM switch 150 is turned off, the protocol processor 121 will deactivatethe SIM using the "Deactivate Switched SIM" procedure. The SIM does nothave to be physically removed. The activate SIM switch 150 can be placedin many locations, including on the TA 36 or on an external device, suchas an MS cradle or cordless telephone base station. This allowsconvenient switching between public and private mode operation. "Publicmode" means that the normal GSM air interface is used to deliver a callto a subscriber. "Private mode" means that a call to a GSM subscriber isdelivered over the wired subscriber loop 37 to a GSM Wired TerminalAdapter.

The ISDN set 112 originates and terminates circuit-switched datacommunications service using normal ISDN data call procedures. The TA 36supports data transfer rates up to 9.6 kbps. The TA 36 also supportshigher data rates by setting up a high-speed circuit-switched data call,using the high speed circuit switched data service specified in the 1996release of the ETSI GSM technical specifications (referred to as GSM96).

TA 36 Location Updates

A location area in a PLMN 12 consists of a group of BTS 28, and eachlocation area has a unique location area identifier. A location area inthe wired environment consists of a group of TAC 34, and each locationarea has a unique location area identifier. A location update message issent from a device (MS 30 or TA 36) to a visitor location register (VLR19) to identify the location area within which the device is currentlyoperating.

When power is applied to the TA 36, mobility logic in the TA 36 willsend a location update message to the VLR 19 in the PLMN 12 for each SIM111a installed in the TA 36. The VLR 19 will pass the location updateinformation to the HLR 18, and both will record location informationassociated with the TA 36. When the activate SIM switch 150 is toggledto "On", mobility logic in the TA 36 will issue a location updatemessage to the VLR 19 for that activated SIM 111b. The TA 36 will alsoissue location update messages for each active SIM 111a and SIM 111b inresponse to periodic location update requests from the VLR 19 whichrequests the VLR 19 issues to refresh its own knowledge of active SIM111.

Seamless Transition from Wireless Operation to Wired Operation

Location update messages are used to identify the location area of theMS 30 (which contains a SIM) and SIM 111b in the TA 36. Seamlesstransition between PLMN 12 wireless and SOHO 16 wired operation isachieved by using duplicate copies of SIM 111b in the MS 30 and switchedSIM interface 125. To switch from wireless operation to wired operation,the MS 30 is powered off, and the activate SIM switch 150 is toggled to"On". The activate SIM switch 150 may be physically located in variousplaces, including on the TA 36, in a battery recharging cradle for theMS 30, or in a cordless telephone base station. As described previously,the TA 36 will send a location update message to the VLR 19 to indicateSIM 111b is active in the TA's 36 location area. After the locationupdate, calls to the MS 30 MSISDN will cause page messages from the MSC20 to be routed to the TA 36. The TA 36 will respond to the pagemessages, and terminate the call to the ISDN set 38 or analog set 118associated with the SIM 111b.

Seamless transition between SOHO 16 wired and PLMN 12 wireless operationoccurs when the activate SIM switch 150 is toggled to "Off", and the MS30 is powered on. This will cause the TA 36 to send a detach message tothe PLMN 12 for SIM 111b. Subsequently, the MS 30 will send a locationupdate message to the BTS 28 in the PLMN 12. When the user carries theMS 30 away from home, calls to the MS 30 MSISDN are delivered to the MS30 as normal mobile terminated calls.

The TA 36 has a semi-permanent SIM 111a installed. A unique MSISDNassociated with the SIM 111s causes calls to the TA 36 MSISDN to berouted to the wired TA 36.

Home, Office, and Public Mobility

The MS 30 is not limited to using only one wired TA 36. For example, asubscriber can place TA's in his residence and office. This subscribermoving from home to office would be able to receive calls via the wiredTA 36 at home, then via the public PLMN 12 in transit, and then, uponupdating location with the wired TA 36 at his office, receive calls athis office via a wired subscriber loop 37.

Alternate Embodiments

The invention is not limited to the GSM standards for digital cellulartelephone service. The invention applies equally well to the followingsystems:

1) Advanced Mobile Phone System (AMPS) analog cellular systems;

2) Time Division Multiple Access (TDMA) (Telecommunications IndustryAssociation (TIA)--TIA IS-54 is the standard for TDMA digital cellularsystems); and

3) Code Division Multiple Access (CDMA) (TIA IS-95 is the standard forCode Division Multiple Access digital cellular systems.)

OPERATION OF THE PREFERRED EMBODIMENT

In operation, the TA 36 provides standard telephony interfaces to analogand ISDN BRI terminals. The TA 36 interworks the standard terminalsignals to GSM Radio interface layer 3 messages and procedures. That is,the signals to the BSC 24 from the BTS 28 and from the TAC 34 appearidentical, as to their format and protocol.

Terminal Adapter (TA 36) Flow Charts (FIGS. 5-9)

The following flow charts describe the logic of the Protocol Processor121 of the GSM Wired Terminal Adapter 36. Protocol errors are handled asdescribed by the appropriate ISDN and GSM specifications.

Terminal Adapter Power On (FIG. 5)

The algorithm shown in FIG. 5 is executed when, in step 301, a powerswitch (not shown) on the terminal adapter 36 is moved to the "On"position. In step 302, the protocol processor 121 first checks if theSubscriber Identity Module (SIM) 111a is installed at the SIM Interface122, and if the SIM 111b is installed at the Switched SIM Interface 125.For each SIM that is installed, the TA 36 follows the normal GSM RadioInterface Layer 3 (RIL3) procedures for performing a location updatewith the GSM Network Switching System's Home Location Register, asdescribed in GSM 4.08, sending the GSM Radio Interface Layer 3 messagesfor Radio Resource (RR) and Mobility Management (MM) on the D-channel ofthe wired subscriber loop 131, connecting the U' Interface 124 of the TA36 to the GSM wired terminal adapter controller 34. The GSM locationupdate procedure enables the GSM network to deliver a call to thedirectory number associated with a SIM to the TA 36 where that SIM isinstalled.

If the protocol processor 121 does not detect the SIM 111a installed atthe SIM interface 122, or the SIM 111b installed at the switched SIMinterface 125, then the protocol processor 121 at step 303 enters astate in which it performs no further processing, until, in step 304, itdoes detect the SIM 111b inserted in the switched SIM interface 125.

The protocol processor 121 then proceeds at step 305 executing the GSMlocation updating procedure. At step 305, the protocol processor 121sends a GSM RIL3- RR channel request message to the TAC 34. In response,in step 306 the protocol processor 121 receives a GSM RIL3- RR channelassignment message from the TAC 34.

Next, in step 307, the protocol processor 121 sends a GSM RIL3- MMlocation update message to the TAC 34. In step 308, the protocolprocessor 121 immediately receives a GSM RIL3- RR LAPD unnumberedacknowledgment (UA) message from the TAC 34.

In step 309, the protocol processor 121 receives a GSM RIL3-MMauthentication request from the TAC 34. In step 310, the protocolprocessor 121 calculates the value for the authentication response,according to normal GSM authentication procedures. In step 311 theprotocol processor 121 sends the GSM RIL3- MM authentication responsemessage to the TAC 34. In step 312, the protocol processor 121 receivesa GSM RIL3- MM location update accepted message from the TAC 34.Following this, in step 313, the protocol processor 121 receives a GSMRIL3- RR channel release message from the TAC 34. In step 314, theprotocol processor 121 checks if there is a SIM installed for which noGSM location update has been sent. If so, the protocol processor 121proceeds to step 305. In step 315, the protocol processor 121 enters astate where it is waiting for a call origination from the ISDN set 38 orthe ISDN adapter 116, a call termination from the TAC 34, deactivationof the activate SIM switch 150, or the TA 36 power switched off.

Terminal Adapter Power Switched Off (FIG. 6)

The protocol processor 121 executes the algorithm in FIG. 6 when, instep 401, the power switch (not shown) of the TA 36 is moved to the offposition. The protocol processor 121 performs the GSM detach procedurefor both SIMs 111a and 111b, which informs the HLR 18 that the directorynumber associated with each SIM can no longer be reached through thenetwork. The TA 36 remains powered until it has completed the GSM detachprocedure. In step 402, the protocol processor 121 sends a GSM RIL3- RRchannel request message to the TAC 34. In response, in step 403 theprotocol processor 121 receives a GSM RIL3- RR channel assignmentmessage. In step 404 the protocol processor 121 then sends a GSM RIL3-MMdetach message for the SIM 111a to the TAC 34. In step 405, the responseto the GSM RIL3-MM detach message is a LAPDm unnumbered acknowledgment(UA) message from the TAC 34, followed, in step 406, by the GSM RIL3-MMauthentication request received. On receipt of the authenticationrequest, the protocol processor 121 in step 407 calculates theauthentication response using the GSM authentication algorithm, and instep 408 sends it to the TAC 34 in a GSM RIL3-MM authentication responsemessage. In step 409, the response from the TAC 34 is a GSM RIL3-MMdetach acknowledgment received by the protocol processor 121. In step410, the protocol processor 121 receives a GSM RIL3-RR channel releasefrom the TAC 34. In step 411, the protocol processor 121 checks if theSIM 111b is installed at the switched SIM interface 125. If it is, theGSM detach procedure is repeated starting at step 402, but this timespecifying the SIM 11b in the GSM RIL3- MM detach message in step 404.In step 412, only after the GSM detach procedure has been completed foreach installed SIM is the power turned off to the TA 36. The TA 36 mustbe powered off prior to removing the SIM 111a from the SIM Interface122. The activate SIM switch 150 must be in the "deactivated" positionprior to removing the SIM 111b from the switched SIM interface 125.

Subscriber Places a Call (FIGS. 7a and 7b)

The algorithm shown in FIG. 7 is executed by the protocol processor 121when the ISDN set 38 or the analog set with ISDN adapter 39 is used bythe subscriber to place a call. From the perspective of the protocolprocessor 121, the analog set with ISDN adapter 39 presents the samecall control signaling interface as the ISDN set 38. Either of thesedevices, when used by the subscriber to place a call, will, in step 450of FIG. 7a, send an ISDN Q.931 setup message via the S/T Bus interface120 to the protocol processor 121, which initiates the call setupprocedure. References to "ISDN set" in FIG. 7 refer to both the ISDN set38 and/or the analog set with ISDN adapter 39.

In step 451, the protocol processor 121 checks if the SIM 111a isinstalled at the SIM interface 122, or if the SIM 111b is installed atthe switched SIM interface 125. If neither the SIM 111a nor the SIM 111bis installed, then in step 452 the protocol processor 121 instructs thevoice service module 123 to provide an audible treatment to thesubscriber. This treatment can be a pre-recorded voice announcementstating that there is no SIM installed, or a standard telephony"reorder" tone. If either the SIM 111a or the SIM 111b is installed,then the protocol processor 121 proceeds to step 453.

When placing a call, the subscriber must press the octothorpe key (#)after dialing the called number. In step 453, the protocol processor 121examines the contents of the ISDN Q.931 setup message. If the ISDN Q.931setup message contains no dialed digits, or if the called party addressin the ISDN Q.931 setup message contains a string of dialed digits thatdoes not end with an octothorpe (#), then in step 454 the protocolprocessor 121 starts an interdigit timer, and collects digits until anoctothorpe (#) is encountered. In step 455, the protocol processor 121determines if the ISDN Q.931 setup message contains dialed digits.

If there are no dialed digits, then in step 457 the protocol processor121 also instructs the voice service module 123 to play dialtone to theISDN set 38 or ISDN adapter 116. In step 459, when the protocolprocessor 121 receives the first digit, then in step 460 it instructsthe voice service module 123 to stop the dial tone. When the protocolprocessor 121 receives a digit in step 458 or in step 459, then in step461 it stops the interdigit timer.

The interdigit timer is normally five seconds, but can be configured toother values. If the interdigit timer expires (step 466) between thereception of individual digits at any time prior to the protocolprocessor 121 receiving an octothorpe, then in step 467 the voiceservice module 123 provides an audible treatment to the ISDN set 38 orISDN adapter 116. This treatment can be a pre-recorded voiceannouncement instructing the subscriber to redial the called number, ora standard telephony "reorder" tone.

Each time the protocol processor 121 receives a digit at step 458 andstep 459, it first stops the interdigit timer at step 461, and then instep 462 checks if the received digit is an octothorpe. If it is not,the protocol processor 121 starts the interdigit timer, and in step 463waits for the next digit.

If the digit is an octothorpe, then, referring to FIG. 7b, the protocolprocessor 121 proceeds with the normal GSM call setup procedure in step468, beginning by sending a GSM RIL3- radio resource channel requestmessage to the TAC 34. If, in step 453 of FIG. 7a, the called partyaddress in the ISDN Q.931 setup message contains a string of dialeddigits ending with an octothorpe (#), then beginning at step 468 in FIG.7b, the protocol processor 121 performs the normal GSM call setupprocedure. In response to the GSM RIL3-RR channel request message, instep 469 the TA 36 receives a GSM RIL3-RR channel assignment. In step470 the protocol processor 121 sends a GSM RIL3-MM CM service request.

The response to the GSM RIL3-MM CM service request is a GSM RIL3-RRLAPDm unnumbered acknowledgment (UA) message received in step 471,followed by the GSM RIL3- MM authentication request received in step472. On receipt of the authentication request, the protocol processor121 calculates the authentication response in step 473 using the GSMauthentication algorithm, and sends it to the TAC in a GSM RIL3- MMauthentication response message in step 474. At this point, the protocolprocessor 121 in step 475 converts the ISDN Q.931 setup message that wasreceived in step 450 into a GSM RIL3-CC setup message, and sends it tothe TAC 34.

Following this, in step 476 the TA 36 receives a GSM RIL3-CC callproceeding message, which the protocol processor 121 converts into anISDN Q.931 call proceeding message. In step 477, the protocol processor121 sends it to the ISDN set 38 or ISDN adapter 116 via the S/T BusInterface120. In a similar fashion, in step 478 the protocol processor121 converts the incoming GSM RIL3-CC alerting message into an ISDNQ.931 alerting message, which, in step 479 is sent to the ISDN set 38 orISDN adapter 116. When the called party answers, in step 480 theprotocol processor 121 converts the resultant incoming GSM RIL3-CCconnect message from the TAC 34 into an ISDNQ.931 connect message, whichin step 481 is passed to the ISDN set 38 or ISDN adapter 116.

In step 482, an ISDN Q.931 connect acknowledgment message is receivedfrom the ISDN set 38 or ISDN adapter 116. In step 483, the protocolprocessor 121 sends a GSM RIL3-CC connect acknowledgment to the TAC 34.In step 484 the protocol processor 121 enters an active call state,waiting for either an ISDN Q.931 disconnect message from the ISDN set 38or ISDN adapter 116, or a GSM RIL3-CC disconnect message from the TAC34.

Subscriber is Called (FIGS. 8a and 8b)

In step 501 the protocol processor 121 waits for a paging request. Thealgorithm shown in FIG. 8 is executed when, in step 502, the TA 36receives a GSM RIL3-RR paging request message from the TAC 34. In step503, the protocol processor 121 checks if the SIM specified in thepaging request is installed at the SIM interface 122 or the switched SIMinterface 125. If the specified SIM is not installed, then the protocolprocessor 121 does not respond to the paging request, but returns tostep 501, where it waits for a paging request.

If the requested SIM is installed at either the SIM interface 122 or atthe Switched SIM Interface 125, then in step 504 the protocol processor121 sends a GSM RIL3-RR channel request to the TAC 34. In step 505, theprotocol processor 121 receives a GSM RIL3-RR channel assignment messagefrom the TAC 34. In step 506, the protocol processor 121 sends a GSMRIL3-RR paging response message to the TAC34, indicating that the pagedSIM is available at the TA 36. The TAC 34 immediately responds with aGSM RIL3-RR LAPD unnumbered acknowledgment (UA) message which, in step507, the Protocol processor 121 receives.

Following this, in step 508 the protocol processor 121 receives a GSMRIL3-MM authentication request from the TAC 34. In step 509 the protocolprocessor 121 calculates the value for the authentication responseaccording to normal GSM authentication procedures. In step 510 theprotocol processor 121 sends the GSM RIL3-MM authentication responsemessage to the TAC 34. In step 511, the protocol processor 121 receivesa GSM RIL3- call control (CC) setup message from the TAC 34. In step512, the protocol processor 121 responds to the TAC 34 with a GSM RIL3-CC call confirmed message, then converts the GSM RIL3-CC Setup messageinto an ISDN Q.931 Setup message and at step 513 sends that to the ISDNset 38 and to the ISDN adapter 116. In step 514, the protocol processor121 receives an ISDN Q.931 call proceeding message from the ISDN set 38and the ISDN adapter 116.

Referring now to FIG. 8b, in step 515, the protocol processor 121receives an ISDN Q.931 alerting message. In step 516, the protocolprocessor 121 sends a GSM RIL3-CC alerting message to the TAC 34. Instep 517, when the protocol processor 121 receives an ISDN Q.931 connectmessage from either the ISDN set 38 or the ISDN adapter 116, in step 518it is converted to a GSM RIL3-CC connect message, which is sent to theTAC 34. In step 519, in response to this message, the TAC 34 sends a GSMRIL3-CC connect acknowledgment message. In step 520, the protocolprocessor 121 converts this to a ISDNQ.931 connect acknowledgmentmessage, and sends it to the ISDN set 38 or the ISDN adapter 116. Instep 521, the protocol processor 121 then enters an active call state,waiting for either an ISDN Q.931 disconnect message from the ISDN set 38or ISDNadapter 116, or a GSM RIL3-CC disconnect message from the TAC 34.

Switched SIM Deactivation (FIG. 9)

The algorithm shown in FIG. 9 is executed when the activate SIM switch150 is set to the "deactivate" position. In step 550 the protocolprocessor 121 detects this change through the switch circuit connection154. In step 551 the protocol processor 121 sends a GSM RIL3-RR channelrequest message to the TAC 34. In response, the protocol processor 121receives a GSM RIL3-RR channel assignment message in step 552. Theprotocol processor 121 then sends a GSM RIL3-MM detach message for theSIM 111b to the TAC 34 in step 553. In step 554, the response to the GSMRIL3- MM detach message is a LAPDm unnumbered acknowledgment (UA)message from the TAC 34, followed by the GSM RIL3-MM authenticationrequest received, in step 555. On receipt of the authentication request,the protocol processor 121 calculates the authentication response instep 556 using the GSM authentication algorithm, and sends it to the TAC34 in a GSM RIL3-MM authentication responsemessage in step 557. In step558, the protocol processor 121 receives a GSMRIL3-MM detachacknowledgment from the TAC 34. Following this, the protocol processor121 receives a GSM RIL3-RR channel release message from the TAC 34 instep 559. In step 560, the protocol processor 121 enters a state inwhich it waits for the activate SIM switch 125 to be switched back tothe "activate" position.

Terminal Adapter Controller (TAC 34) Flow Chart (FIG. 10)

The algorithms of the TAC 34 are shown in FIG. 10. When the TAC 34receives a message from the BSC 24 in step 602, the TA controllerapplication 214 checks in step 603 whether the message is from the TA 36or from the BSC 24. If from the TA 36, in step 604 the TA controllerapplication 214 checks if it is a GSM RIL3-RR channel request message.If not, the TA controller application 214 relays the message unalteredto the BSC 24 in step 605, and proceeds to step 601, where it waits forthe next incoming message.

If the message in step 604 is a GSM RIL3-RR channel request message,then in step 609 the TA controller application 214 stores informationfrom the message that it needs to properly switch the traffic channelconnection. The TA controller application 214 then sends the messageunaltered to the BSC 24 in step 610, and proceeds to step 601, where itwaits for the next incoming message.

At step 603, if the message is from the BSC 24, then the TA controllerapplication 214 checks in step 606 if it is a GSM RIL3-RR channelassignment message, a GSM RIL3- channel release message, a GSM RIL3-RRcipher mode message, or a GSM RIL3-RR paging request. If it is not oneof these, the TA controller application 214 relays the message unalteredto the TA 36 in step 607, and proceeds to step 601 where it waits forthe next incoming message. If the TA Controller Application 214 isprocessing a GSM RIL3- RR channel assignment message, it storesinformation from the message in step 613 that it needs to properlyswitch the traffic channel connection. It then relays the messageunaltered to the TA 36 in step 614, and proceeds to step 601 where itwaits for the next incoming message.

In step 606, if the message is a GSM RIL3-RR channel release message,the TA controller application 214 clears the information for switchingthe traffic channel connection associated with that message in step 616.It then relays the message unaltered to the TA 36 in step 617, andproceeds to step 601 where it waits for the next incoming message. Instep 606, if the message is a GSM RIL3- RR paging request message, thenin step 619 the TA Controller application 214 broadcasts the message toall TA's 36 which are connected to the TAC 34. The TA Controllerapplication 214 then proceeds to step 601 where it waits for the nextincoming message.

In step 606, if the message is a GSM RIL3-RR cipher mode, then the TAcontroller application 214 sends a GSM RIL3- RR cipher mode completemessage to the BSC 24 in step 621. The GSM RIL3-RR cipher mode messageis not relayed to the TA 36. The TA controller application 214 thenproceeds to step 601 where it waits for the next incoming message.

Although an illustrative embodiment of the invention has been shown anddescribed, other modifications, changes, and substitutions are intendedin the foregoing disclosure. Accordingly, it is appropriate that theappended claims be construed broadly and in a manner consistent with thescope of the invention.

What is claimed is:
 1. A system to enable communication between a basestation controller within a cellular network, and a wired telephonesystem in a wired subscriber loop, wherein the base station controlleris responsive to, and generates, cellular network signaling, and thewired telephone system is responsive to, and generates, wired signals,the system comprising:a. means for converting wired signals to cellularnetwork signaling; b. means for converting mobility events in the wiredtelephone system to cellular network signaling; c. means for providingthe cellular network signaling to the base station controller so thatthe cellular network may respond to the provided cellular networksignaling according to cellular network signaling techniques; and d.means for enabling said base station controller to locate a subscriberin said wired telephone network.
 2. The system of claim 1, wherein thecellular network signaling is GSM signaling.
 3. The system of claim 1,wherein the cellular network signaling is Advanced Mobile Phone Systemsignaling.
 4. The system of claim 1, wherein the cellular networksignaling is Time Division Multiple Access signaling.
 5. The system ofclaim 1, wherein the cellular network signaling is Code DivisionMultiple Access signaling.
 6. The system as in any of claims 1-5,further comprising means for compressing voice data to standard cellularcompression.
 7. A system according to claim 1 further comprising:a firsttelephone coupled to said wired telephone system; and a second telephonecoupled to said wired telephone system.
 8. A system according to claim 7wherein said means for enabling comprises subscriber informationrelating to said subscriber including an associated telephone number. 9.A system according to claim 8 wherein said first telephone and saidsecond telephone are capable of receiving said subscriber information.10. A system according to claim 9 wherein said base station controllerassociates said subscriber with said first telephone when saidsubscriber information is received by said first telephone.
 11. A systemaccording to claim 10 wherein said base station controller associatessaid subscriber with said second telephone when said subscriberinformation is received by said second telephone.
 12. A system accordingto claim 11 wherein said base station controller provides communicationsfor said telephone number to said first telephone when said subscriberinformation is associated therewith.
 13. A system according to claim 12wherein said base station controller provides communications for saidtelephone number to said second telephone when said subscriberinformation is associated therewith.
 14. A method of enablingcommunication between a base station controller within a cellularnetwork, and a wired telephone system in a wired subscriber loop,wherein the base station controller is responsive to, and generates,cellular network signaling, and the wired telephone system is responsiveto, and generates, wired signals, the method comprising:a. convertingwired signals to cellular network signaling; and b. converting mobilityevents in the wired telephone system to cellular network signaling; andc. transmitting the cellular network signaling to the base stationcontroller so that the base station controller may respond to thetransmitted cellular network signaling; and d. enabling said basestation controller to locate a subscriber in said wired telephonenetwork.
 15. The method of claim 14, wherein the cellular networksignaling is GSM signaling.
 16. The method of claim 14, wherein thecellular network signaling is Advanced Mobile Phone System signaling.17. The method of claim 14, wherein the cellular network signaling isTime Division Multiple Access signaling.
 18. The method of claim 14,wherein the cellular network signaling is Code Division Multiple Accesssignaling.
 19. The method of any of claims 14-18, further comprisingmeans for compressing voice data to standard cellular compression.
 20. Amethod according to claim 14 further comprising the steps of:coupling afirst telephone to said wired telephone system; and coupling a secondtelephone to said wired telephone system.
 21. A method according toclaim 20 further comprising the step of receiving said subscriberinformation by said first telephone and said second telephone.
 22. Amethod according to claim 21 wherein said step of enabling comprises thestep of storing subscriber information relating to said subscriberincluding an associated telephone number.
 23. A method according toclaim 21 further comprising the steps of:associating said subscriberwith said first telephone when said subscriber information is receivedby said first telephone; and associating said subscriber with saidsecond telephone when said subscriber information is received by saidfirst telephone.
 24. A method according to claim 23 further comprisingthe steps of:providing communications for said telephone number to saidfirst telephone when said subscriber information is associatedtherewith; and providing communications for said telephone number tosaid second telephone when said subscriber information is associatedtherewith.
 25. A system to enable communication between a base stationcontroller within a cellular network, and a wired telephone system in awired subscriber loop, wherein the base station controller is responsiveto, and generates, cellular network signaling between a wirelesstelephone and a mobile services switching center, and the wiredtelephone system is responsive to, and generates, wired signals to andfrom a wired telephone, the system comprising:a. a terminal adaptercontroller conductively coupled to the base station controller, andreceptive to the cellular network signaling, for generating processedsignals; b. a protocol processor conductively coupled both to the wiredtelephone system and to the terminal adapter controller, receptive tothe processed signals, for generating wired signals; and c. a module forenabling said base station controller to locate a subscriber within saidwired telephone systemwhereby the base station controller is responsiveto, and generates, cellular network signaling between the wiredtelephone and the mobile services switching center so that the telephonebeing wired is relatively transparent to the mobile services switchingcenter.
 26. The system of claim 25, wherein the cellular networksignaling is GSM signaling.
 27. The system of claim 25, wherein thecellular network signaling is Advanced Mobile Phone System signaling.28. The system of claim 25, wherein the cellular network signaling isTime Division Multiple Access signaling.
 29. The system of claim 25,wherein the cellular network signaling is Code Division Multiple Accesssignaling.
 30. The system as in any of claims 25-29, further comprisinga voice service module conductively coupled to the protocol processor,for compressing voice data to standard cellular compression.